package com.eascs.common.crypto;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Base64;

import com.eascs.common.exception.RuntimeIOException;

/**
 * <p>
 * BASE64编码解码工具包
 * </p>
 * <p>
 * 依赖javabase64-1.3.1.jar
 * </p>
 * 
 */
public class Base64Utils {

	/**
	 * 文件读取缓冲区大小
	 */
	private static final int CACHE_SIZE = 1024;

	/**
	 * <p>
	 * BASE64字符串解码为二进制数据
	 * </p>
	 * 
	 * @param base64
	 * @return
	 * @throws Exception
	 */
	public static byte[] decode(String base64) {
		return Base64.getDecoder().decode(base64.getBytes());
	}

	/**
	 * <p>
	 * 二进制数据编码为BASE64字符串
	 * </p>
	 * 
	 * @param bytes
	 * @return
	 * @throws Exception
	 */
	public static String encode(byte[] bytes) {
		return new String(Base64.getEncoder().encode(bytes));
	}

	/**
	 * <p>
	 * 将文件编码为BASE64字符串
	 * </p>
	 * <p>
	 * 大文件慎用，可能会导致内存溢出
	 * </p>
	 * 
	 * @param filePath
	 *            文件绝对路径
	 * @return
	 * @throws Exception
	 */
	public static String encodeFile(String filePath) {
		byte[] bytes = fileToByte(filePath);
		return encode(bytes);
	}

	/**
	 * <p>
	 * BASE64字符串转回文件
	 * </p>
	 * 
	 * @param filePath
	 *            文件绝对路径
	 * @param base64
	 *            编码字符串
	 * @throws Exception
	 */
	public static void decodeToFile(String filePath, String base64) {
		byte[] bytes = decode(base64);
		byteArrayToFile(bytes, filePath);
	}

	/**
	 * <p>
	 * 文件转换为二进制数组
	 * </p>
	 * 
	 * @param filePath
	 *            文件路径
	 * @return
	 * @throws Exception
	 */
	public static byte[] fileToByte(String filePath) {
		byte[] data = new byte[0];
		File file = new File(filePath);
		if (file.exists()) {
			ByteArrayOutputStream out = new ByteArrayOutputStream(2048);
			try {
				FileInputStream in = new FileInputStream(file);
				byte[] cache = new byte[CACHE_SIZE];
				int nRead = 0;
				while ((nRead = in.read(cache)) != -1) {
					out.write(cache, 0, nRead);
					out.flush();
				}
				out.close();
				in.close();
			} catch (IOException e) {
				throw new RuntimeIOException(e);
			}
			data = out.toByteArray();
		}
		return data;
	}

	/**
	 * <p>
	 * 二进制数据写文件
	 * </p>
	 * 
	 * @param bytes
	 *            二进制数据
	 * @param filePath
	 *            文件生成目录
	 */
	public static void byteArrayToFile(byte[] bytes, String filePath) {
		InputStream in = new ByteArrayInputStream(bytes);
		File destFile = new File(filePath);
		if (!destFile.getParentFile().exists()) {
			destFile.getParentFile().mkdirs();
		}
		try {
			destFile.createNewFile();
			OutputStream out = new FileOutputStream(destFile);
			byte[] cache = new byte[CACHE_SIZE];
			int nRead = 0;
			while ((nRead = in.read(cache)) != -1) {
				out.write(cache, 0, nRead);
				out.flush();
			}
			out.close();
			in.close();
		} catch (IOException e) {
			throw new RuntimeIOException(e);
		}
	}

}